Initial studies suggest that T cell lines CCRF-CEM and HSB-2 share tumor specific antigens with tumor cells from children with T cell leukemia. We propose to confirm and extend these findings. Tumor cell and control cell suspensions will be tested for specific reactivity with Tymocyte and B cell line absorbed sera from rabbits immunized with T cell lines by a) direct cytotoxicity using 51Cr release and/or Trypan blue uptake, and b) absorption of cyctotoxic activity. KCI extracts of T cell lines will be examined for presence of T cell leukemia antigens by testing their ability to absorb tumor specific reactivity of rabbit antisera. Attempts will then be made to purify and characterize such soluble antigens by column chromatography, analytical gel electrophoresis. Both intact cells and soluble extracts of T cell lines will be further tested for tumor antigens by determining whether children with T cell leukemia are specifically responsive or unresponsive to them. (Control subjects will be similarly tested.)Cellular responsiveness will be measured by in vitro lymphocyte blastogenesis and cell mediated cytotoxicity. Humoral reactivity will be assayed by immunofluorescence and radioimmunodiffusion.